This is a summary of preliminary results from a lab-scale experiment investigating the suitability of black soldier fly frass as co-substrate in anaerobic digestion of cattle slurry. The experiment was conducted from December 2020 to February 2021 at the Department of Microbiology, University of Innsbruck. The frass was obtained from an industrial-scale rearing experiment, during which different pre-treatment options for improved larval bioconversion of agro-industrial wastes were investigated.